The present invention relates to a door-latch apparatus and, more particularly, to a door-latching mechanism for the sliding door of a motor vehicle.
Door latching apparatus, specifically for a vehicle sliding door, is disclosed in the U.S. Pat. No. 3,929,361 to Horst Klebba. This mechanism includes a turning latch, rotatable between a closed and an open position, rigidly connected with a blocking lever having a tab which extends into a slot in a pivot lever. A spring biases the pivot lever in a direction urging the blocking lever, and thereby the turning latch, into the open position. A movable operating lever has a contact area arranged in sliding contact with first and second surfaces of the pivot lever such that when the turning latch is in an open position, the contact area is in contact with the first edge surface, thereby releasing the pivot lever, and when the turning latch is in a closed position, the contact area is in contact with the second edge surface, thereby locking the pivot lever. A second spring biases the operating lever in a direction urging the operating lever into the position in which the pivot lever is locked.
In this particular door-latching mechanism, both the angle at which the two edge surfaces of the pivot lever meet and the angle formed by the contact area of the operating lever are acute angles. When turned to the open position, the acute-angled edge surfaces of the pivot lever slip into a cut-out below the acute-angled contact area of the operating lever, while in the opposite case, when the turning latch is in the closed position, the contact area of the operating lever holds the acute-angled edge surface of the pivot lever.
In a door latching mechanism of this general type there is a danger that the turning latch will return to the closed position when it should be caused to open. Because of friction, the contact area of the operating lever cannot slide freely over the edge surfaces of the pivot lever. This friction produces a torque about the pivot shaft of the pivot lever which counteracts the motion of the pivot lever from the closed position to the open position when the turning latch moves. In the case of the door latch according to the above-noted patent, this resistance to opening is prevented by providing a suitable bend in the first edge surface of the pivot lever such that the force exerted on it by contact area of the operating lever produces a torque in the direction of opening.